Traction Hydro Drive Issue

[bobsphotos]

I have some type of Drive issue going on with my 3320. I changed the hydro filter and oil in the fall and I had the feeling something was different but couldn't really put my finger on what it was. Between the oil change and now i really haven't worked the tractor until this weekend trying to push some snow banks back. I have a small hill going to the back of my property and have always been able to drive right up it in "B" range. When I try now, the rear wheels just stop driving and it makes kind of a growling noise. If I back off on the throttle and then push back down it will start moving again. I thought low range was OK, but I tried going out back in about a foot of snow in Low range \ 4 wheel drive, and the same issue happened.
The rear tires have chains on them but I don't see how this could be the issue. Last year I skidded logs out with this tractor set up the same way so I am at a loss.
The hydro oil level is fine and when it stops driving the rear wheels, I have full bucket hydraulics. When I did the oil change, I also cleaned the inline filter.
Any opinions or suggestions will be appreciated.

 

[DFB]

Did you use JD low viscosity hydraulic fluid when you changed the oil and filter?

 

[bobsphotos]

Yes, and the John Deere brand filter.

 

[oldnslo]

Growling sound could be from pump cavitation. Not sure how the charge pump is connected on your tractor but I would definitely start looking at parts diagrams to figure out where air could be entering the system. Check any inlet hoses for loose connections, cracks in hoses, etc. Running it like this will severely shorten the life of a HST.

Note: It is possible to have vacuum leaks and not show any external oil leakage.

 

[arlen4720]

Did you clean the suction screen when you changed the filter?

 

[DFB]

I'll just throw this one out there because it happens a lot to us at the orchard especially with the M9000 Kubota and the 2855 JD. When of them wont climb the hill or seems like there is no power we find the parking brake hung up or the wasn't fully released

 

[bobsphotos]

Did you clean the suction screen when you changed the filter?

I checked with a mechanic at the Deere dealership and he said there is no suction screen on my tractor. I asked specifically, because I had seen comments in posts referring to a suction screen. If someone can point me to a screen, that would be awesome.